The present disclosure generally relates to an anion exchange composite membrane filled with crosslinked polymer electrolytes for fuel cells and method for preparing the same, and more particularly, to a technique for preparing an anion exchange composite membrane filled with crosslinked polymer electrolytes having high ion exchange capacity and hydroxyl ion conductivity in spite of using a small content of electrolyte monomers.
The fuel cells are provided with fuel and air to generate electrical energy. There are some advantages in the fuel cells in that they have high efficiency and generate low environmental pollutants such as exhaust emissions when used. Moreover, a limited quantity of energy is charged in conventional primary cells and secondary cells charge and then it is discharged, whereas the fuel cells are continuously provided with fuel, so the generation is maintaining. Therefore, Many studies on the fuel cells have been performed as a next generation clean energy.
An ion exchange membrane is a type of plastic membrane for separation, which can separate an anion or a cation selectively depending on an ion exchangeable group introduced in the membrane. In a cation exchange membrane being used commercially, the ion exchangeable group is largely divided into a sulfonic acid group (—SO3-) and a carboxylic acid group (—COO—). The former is strong acid and the latter is weak acid. On the other hand, in an anion exchange membrane, the ion exchangeable group is mainly a quanternary ammonium group (—N+R3) which is strong alkali.
This ion exchange membrane is used in electrolysis for desalinizing and refining, water-splitting electrolysis, diffusion dialysis extracting acid from acid waste liquor, and electrodeionization for producing de-ionized water etc. Moreover, after a recent report that there is a probability of using an anion exchange membrane in fuel cells, studies on using an anion exchange membrane in fuel cells are on the increase.
The fuel cells have an anode and a cathode. The former can be provided with hydrogen ions and electrons from hydrogen and methanol, whereas the latter can be provided with oxygen. The principle of generating electricity from fuel cells is as below. That is, when fuel is provided through the anode, it is divided into hydrogen ions and electrons, and then the hydrogen ions are combined with oxygen provided from the cathode through an electrolyte membrane, and then the electrons separated from the fuel of the anode pass through an external circuit. As a result, electric currents are generated, and an electrochemistry reaction, i.e. an inverse reaction of electrolysis of water progresses to generate electricity, heat and water. This types of fuel cells are, for example, polymer electrolyte membrane fuel cell (PEMFC), direct methanol fuel cell (DMFC), direct borohydride fuel cell (DBFC) and solid alkaline fuel cell (SAFC) etc. The PEMFC, DMFC and DBFC of the fuel cells employ a cation exchange membrane that is cation or hydrogen ion conductive electrolyte membrane as a electrolyte membrane, whereas the SAFC or the DBFC of the fuel cells employs an anion exchange membrane that is hydroxyl ion conductive electrolyte membrane as a electrolyte membrane. Here, the DBFC can employ both the cation exchange membrane and the anion exchange membrane.
Thus, when compared with the electrolyte cells employing the cation exchange membrane, the electrolyte cells employing the anion exchange membrane has a characteristic to be able to use catalysts of non-noble metals or non-platinum in an electrode, thereby being lower cost. Therefore, studies on preparing the anion exchange membrane in order to develop this fuel cells employing the anion exchange membrane are gradually on the increase.
KR Patent Application No. 1982-0005057 discloses an anion exchange membrane, wherein 10˜90% of anion exchange groups of homogeneous type anion exchange membrane is crosslinked by chain-like aliphatic series of 3˜10 carbons between bonding. The present inventors have developed and applied a method for preparing a polymer electrolyte composite membrane crosslinked by a water-soluble monomer (KR Patent Application No. 10-2008-0110985). However, the above application discloses a cation exchange membrane, and a method for preparing an acrylate monomer-acrylamide crosslinked polymer electrolyte composite membrane having a sulfonic acid group, the polymer electrolyte composite membrane being prepared by impregnating a microporous polymer supporter membrane in mixed solution, the mixed solution containing acrylate monomers having the sulfonic acid group, a bisacrylamid crosslinker and a photo initiator, and then crosslinking with heat or photo.
Therefore, the present inventors have continuously studied on preparing an anion exchange polymer electrolyte composite membrane representing high ion exchange capacity while using a small content of electrolyte monomer, and resulted in completing the present disclosure.